Types of EAS Systems
Magnetic or magneto-harmonic
This systems is designed with the use of tags made from strips of amorphous metal and have a very low magnetic saturation value, an amorphous metal is one such metallic material which has a disorderly atomic-scale structure when compared to most other metal materials, which are crystalline and therefore have a higher ordered arrangement of atoms, amorphous alloys are non-crystalline (metglas) that has a very low magnetic saturation value. In the case of permanent tags, this strip is also lined with a strip of ferromagnetic. Ferromagnetism is the simple mechanism of forming permanent magnets and/or exhibit strong interactions with magnets; it is responsible for most phenomena of magnetism encountered in everyday life.
Detection of the tag is achieved with a transmitter and receiver.
When the ferromagnetic material is magnetized, it biases the amorphous metal strip into saturation, which results in a situation which no longer produces harmonics and Deactivation of these tags are done with magnetization. Activation requires of these tags is done by demagnetization. The system of deactivate and re-activate this type of system is most beneficial and useful to libraries.
Acousto-magnetic or Magnetostrictive
Ferromagnetism is a mechanism by which certain materials form permanent magnets and/or exhibit strong interactions with magnets, it is one of the most commonly used type of magnetism encountered in our everyday life known as the amorphous metal and an amorphous metal is a metallic material that has a disordered atomic-scale structure when compared to most metals, which are crystalline and therefore have a highly ordered arrangement of atoms, amorphous alloys are non-crystalline and a strip of a magnetically semi-hard metallic strip, which is used as a biasing magnet (to increase signal strength) and to allow deactivation. These strips are not bound together but free to oscillate mechanically . The Amorphous metals are commonly used in such systems as they are a great magnetoelastic coupling, meaning they can efficiently convert or transform magnetic energy to mechanical vibrations. The detectors for such tags emit periodic tonal bursts at about 58 kHz, the same as the resonance. At these frequency point, small periodic driving forces are capable of producing large amplitude vibrations as a result of the system frequency in the amorphous trips. This makes the strip to vibrate longitudinally by magnetostriction, and continues to oscillate after the burst is over. The vibration causes a change in magnetization in the amorphous strip, which induces an AC voltage in the receiver antenna and ff this signal meets the required parameters (correct frequency, repetition etc.) the alarm will be activated creating a trigger. The tag can be deactivated by demagnetizing the strip, and the response will be minor ensuring the detector does not detect.
Radio Frequency
Electromagnetism is the physics of the electromagnetic field, a field that exerts a force on particles with the property of electric charge and is reciprocally affected by the presence and motion of such particles field at the resonant frequency which will induce voltages exceeding the capacitor's breakdown voltage. The breakdown voltage of an Insulator is the minimum voltage that causes a portion of an insulator to become electrically conductive. The breakdown voltage of a diode is the minimum reverse voltage to make the diode conduct in reverse which is artificially reduced by puncturing the tags
Microwave
The term usually refers to a semiconductor diode, the most common type available today. At the exit point, one antenna will emits a low-frequency (about 100 kHz) field, and the other will emit a microwave field, the tag then acts as a mixer taking in a combination of signals from both fields an this modulated then signals a trigger in the alarm. These tags are permanent but above the market price of the other tags an most commonly used in clothing stores and other retail outlets.